Emergence of highly-ordered hierarchical nanoscale aggregates on electrostatic binding of self-assembled multivalent (SAMul) cationic micelles with polyanionic heparin

We report three surfactants, with cationic N,N-di-(3-aminopropyl)-N-methylamine (DAPMA) head groups and aliphatic chains connected via an amide linkage, and investigate their ability to self-assemble and bind polyanionic heparin – a process of potential clinical importance in coagulation control. Modifying the hydrophobic chain length tunes the self-assembly event, with C16-DAPMA having the lowest critical micelle concentration and also being the optimal heparin binder. Remarkably highly structured hierarchical nanoscale aggregates are formed on binding between the spherical cationic micelles and linear polyanionic heparin. C14-DAPMA and C16-DAPMA yield organized polycrystalline assemblies as observed by transmission electron microscopy (TEM), predicted in solution by mesoscale simulations and characterized by small-angle X-ray scattering (SAXS). This confirms that the micelles remain intact during the hierarchical assembly process and become packed in a face-centered cubic manner. The nanoscale assembly formed by C16-DAPMA showed the highest degree of order. Importantly, these studies indicate the impact of hydrophobic modification on self-assembly and heparin binding, demonstrate remarkably high stability of these self-assembled micelles even when forming strong electrostatic interactions with heparin, and provide structural insights into nanoscale hierarchical electrostatic assemblies

Cationic polymers for DNA origami coating - examining their binding efficiency and tuning the enzymatic reaction rates

DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The effect of the polymer structure on the binding was investigated and the toxicity of the polymer-origami complexes evaluated. The study shows that all of the analyzed polymers had a suitable binding efficiency irrespective of the block structure. It was also observed that the toxicity of polymer-origami complexes was insignificant at the biologically relevant concentration levels. Besides brick-like DNA origamis, tubular origami carriers equipped with enzymes were also coated with the polymers. By adjusting the amount of cationic polymers that cover the DNA structures, we showed that it is possible to control the enzyme kinetics of the complexes. This work gives a starting point for further development of biocompatible and effective polycation-based block copolymers that can be used in coating different DNA origami nanostructures for various bioapplications.Peer reviewe

Molecular profile of the rat peri-infarct region four days after stroke: Study with MANF

The peri-infarct region after ischemic stroke is the anatomical location for many of the endogenous recovery processes, and the molecular events in the peri-infarct region remain poorly characterized. In this study, we examine the molecular profile of the peri-infarct region on post-stroke day four, time when reparative processes are ongoing. We used a multiomics approach, involving RNA sequencing, and mass spectrometry-based proteomics and metabolomics to characterize molecular changes in the peri-infarct region. We also took advantage of our previously developed method to express transgenes in the peri-infarct region where self-complementary adeno-associated virus (AAV) vectors were injected into the brain parenchyma on post-stroke day 2. We have previously used this method to show that mesencephalic astrocyte-derived neurotrophic factor (MANF) enhances functional recovery from stroke and recruits phagocytic cells to the peri-infarct region. Here, we first analyzed the effects of stroke to the peri-infarct region on post-stroke day 4 in comparison to sham-operated animals, finding that stroke induced changes in 3345 transcripts, 341 proteins, and 88 metabolites. We found that after stroke genes related to inflammation, proliferation, apoptosis, and regeneration were upregulated, whereas genes encoding neuroactive ligand receptors and calcium-binding proteins were downregulated. In proteomics, we detected upregulation of proteins related to protein synthesis and downregulation of neuronal proteins. Metabolomic studies indicated that in after stroke tissue there is increase in saccharides, sugar phosphates, ceramides and free fatty acids and decrease of adenine, hypoxantine, adenosine and guanosine. We then compared the effects of post-stroke delivery AAV1-MANF delivery to AAV1-eGFP (enhanced green fluorescent protein). MANF administration increased the expression of 77 genes, most of which were related to immune response. In proteomics, MANF administration reduced S100A8 and S100A9 protein levels. In metabolomics, no significant differences between MANF and eGFP treatment were detected, but relative to sham surgery group, most of the changes in lipids were significant in the AAV-eGFP group only. This work describes the molecular profile of the peri-infarct region during recovery from ischemic stroke, and establishes a resource for further stroke studies. These results provide further support for parenchymal MANF as a modulator of phagocytic function.Peer reviewe

Automated design of DNA origami

Peer reviewe

Double-degradable responsive self-assembled multivalent arrays-temporary nanoscale recognition between dendrons and DNA

This article reports self-assembling dendrons which bind DNA in a multivalent manner. The molecular design directly impacts on self-assembly which subsequently controls the way these multivalent nanostructures bind DNA-this can be simulated by multiscale modelling. Incorporation of an S-S linkage between the multivalent hydrophilic dendron and the hydrophobic units responsible for self-assembly allows these structures to undergo triggered reductive cleavage, with dithiothreitol (DTT) inducing controlled breakdown, enabling the release of bound DNA. As such, the high-affinity self-assembled multivalent binding is temporary. Furthermore, because the multivalent dendrons are constructed from esters, a second slow degradation step causes further breakdown of these structures. This two-step double-degradation mechanism converts a large self-assembling unit with high affinity for DNA into small units with no measurable binding affinity-demonstrating the advantage of self-assembled multivalency (SAMul) in achieving highly responsive nanoscale binding of biological targets